对象转为JSon

首先将对象转化为Map集合，然后再进行json字符串的转化。List与Map集合可嵌套使用

@Override
    public String getChose(String choseId) {
        // TODO Auto-generated method stub      
        List<ChoseSubjectModel> csList=choseSubjectDao.findeChoseSubjectByChoseId(choseId);     
        @SuppressWarnings("rawtypes")
        List<Map> mapList=new ArrayList<Map>();//LIST<MAP>集合用来存放所有的课程
        for(ChoseSubjectModel cs:csList){
            Map<String,Object> map=new HashMap<String,Object>();//用来存放单独的课程
            SubjectModel subject=cs.getSubject();
            Map<String,Object> subjectMap=new HashMap<String,Object>();//存放一门课程的详细信息
            subjectMap.put("subject",subject.getSubject());
            subjectMap.put("teacher", subject.getTeacher());
            subjectMap.put("subjectTime", subject.getSubjectTime());
            subjectMap.put("subjectAddress", subject.getSubjectAddress());
            map.put("subject", subjectMap); //将课程的详细信息存入 课程中
            mapList.add(map);           //将每门课程存入集合中 
        }
        String str=null;
        try {
            str = new ObjectMapper().writeValueAsString(mapList);//转化为JSON字符串
        } catch (Exception e) {
            e.printStackTrace();
        }

        return str;

    }